Gastric acid is a digestive fluid, formed in the stomach. It is composed of hydrochloric acid (HCl) 0.05–0.1 M (roughly 5,000–10,000 parts per million) potassium chloride (KCl) and sodium chloride (NaCl). The acid plays a key role in digestion of proteins, by activating digestive enzymes, and making ingested proteins unravel so that digestive enzymes break down the long chains of amino acids. The highly acidic environment in the stomach lumen causes proteins from food to lose their characteristic folded structure (or denature). This exposes the protein's peptide bonds. The gastric chief cells of the stomach secrete enzymes for protein breakdown (inactive pepsinogen, and in infancy rennin). Hydrochloric acid activates pepsinogen into the enzyme pepsin, which then helps digestion by breaking the bonds linking amino acids, a process known as proteolysis. In addition, many microorganisms have their growth inhibited by such an acidic environment, which is helpful to prevent infection. HCl is digestive juice. Fatty acids are digested by bile acids.

Iodine test is used to distinguish between the presence of starch and glycogen and other saccharides.
When starch solution is treated with iodine, it gives a blue color. The blue color develops because of the trapping of iodine in the helical coils of amylose. When this test solution is heated, the color disappears due to disruption of the helical coils of amylose and the color reappears upon cooling, due to the reformation of helical coils. Glycogen however gives red color with iodine.
Therefore, the correct answer is option B.

• Raw potato contains approximately 17% starch. when iodine solution added to the raw potato sample, it turns blue-black. Iodine reacts with the starch present in the raw potato which results in the formation of blue-black colored complex. 

When two drops of copper sulphate and ten drops of caustic soda or NaOH is added to egg, it turns violet. This indicates the presence of proteins.
This is Biuret's test and the principle is simple as follows:
In the presence of alkaline medium (caustic soda or NaOH), the Cu2+ ions get reduced to Cu+ and binds to the egg proteins, thereby giving a violet color.
Therefore, the correct answer is option B.

Shake or crush the food to make it dissolve. Filter or dilute the food and ethanol mix so that you get a clear liquid (a solution of fat in ethanol). Add this to a test tube of water. A white (milk-like) emulsion indicates the presence of fats or oils.

The iodine test is used to test for the presence of starch. Iodine dissolved in an aqueous solution of potassium iodide reacts with the starch, producing a purple-black colour. The intensity of the colour decreases with increasing temperature and with the presence of water-soluble organic solvents, such as ethanol.

A chemical test for starch is to add iodine solution (red) and see if it turns blue/black in colour. It is possible to distinguish starch from other carbohydrates using this iodine solution test. For example, if iodine is added to an peeled potato then it will turn black. 

The Biuret test is a chemical test used for detecting the presence of peptide bonds. In the presence of peptides, a copper (II) ion forms violet-coloured coordination complexes in an alkaline solution. The Biuret reaction can be used to assess the concentration of proteins because peptide bonds occur with the same frequency per amino acid in the peptide. 

If an animal needed to store energy for long-term use, but not be encumbered with the weight of extra tissue, then high-calorie fat molecules are the best molecules for storage. So, the correct answer is "high-calorie fat molecules".

A.Leaching - the loss of water-soluble plant nutrients from the soil. It does not help in nutrient conservation.

B.Mineralisation – The process of formation of minerals from the organic compounds is called mineralisation. It helps in nutrient conservation.

C.Nitrification – Formation of nitrites or nitrates from ammonia or nitrogenous compounds is called Nitrification. It also helps in nutrient conservation.

D. Immobilisation – elements, cannot be transported from one place to another place in the body is called Immobilisation and the elements are called Immobilised elements.

So, the correct option is ‘Mineralisation or Nitrification’. 

Amylase is a protein enzyme, a polymer of amino acids. Glycogen is homopolysaccharide of D-glucose with highly branched structure (every 8-12 residues as compared to presence of branches in starch for every 24-30 residues). Phopholipids have phosphate and lipids (carbon and hydrogen atoms) while polysaccharides are polymer of simple sugars. RNA is polymer of ribonucleotides. 

Proteins are the building blocks, which takes part in several metabolic reaction. They have four different levels of structure primary, secondary, tertiary and quaternary. There are 20 different standard L-α-amino acids used by cells for protein construction. Amino acids contain both a basic amino group and an acidic carboxyl group. This difunctionality allows the individual amino acids to join together in long chains by forming peptide bonds: amide bonds between the -NH2 of one amino acid and the -COOH of another. Sequences with fewer than 50 amino acids are generally referred to as peptides, while the terms protein or polypeptide are used for longer sequences. A protein can be made up of one or more polypeptide molecules. The end of the peptide or protein sequence with a free carboxyl group is called the carboxy-terminus or C-terminus. The terms amino-terminus or N-terminus describe the end of the sequence with a free α-amino group. The amino acids differ in structure by the substituent on their side chains. These side chains confer different chemical, physical and structural properties to the final peptide or protein.
So, the correct answer is option B.

Amino acids are the building blocks of polypeptide chain or proteins. These are encoded by the triplet codons of mRNA. Each codon synthesizes a specific amino acid. Example: AUG for methionine, UUU for phenylalanine and so on. Amino acids are connected via the peptide bonds to form the proteins.

Proteins are the polymers of amino acids linked with peptide bonds and perform various functions like carrier, enzyme or hormone. It is considered the most diverse molecule and differs from animal to animal. The diversity in proteins occurs due to the R group present which changes with the change in the amino acid.

a) Glycerol has chemical formula of  C$ _3$H$ _8$O$ _3$. 3 OH groups act as binding site. The carboxyl end of the fatty acid combines with the three -OH groups of the glycerol to form ester. The statement is true.

Proteins are large biomolecules, or macromolecules, consisting of one or more long chains of amino acid residues. Amino acids are Linked by peptide bonds to form polypeptide chains. Proteins are linear polymers formed by linking the α-carboxyl group of one amino acid to the α-amino group of another amino acid with a peptide bond (also called an amide bond).

An amino acid is the structural and functional unit of protein and are made up of carbon, hydrogen, oxygen, nitrogen and sometimes sulphur. These are organic acids with a carboxyl group and one amino group.  Amino acid acts as a buffer.